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ABSTRACT Internal combustion engines (ICEs) can be used in power plants to ensure flexibility in electricity generation. The use of carbon‐free fuels, such as hydrogen and ammonia, in ICEs is a way to decrease greenhouse gas emissions gradually until new carbon‐neutral technology has been fully implemented. By mixing small amounts of these compounds into natural gas (NG), the gas quality requirements can still be achieved and the modification work on the engine can be minimized. In this study, the CO2eq emission intensity was calculated for different NG compositions blended with hydrogen or ammonia while the mixture was within the gas quality specifications. The results showed that the addition of ammonia reduces the CO2eq emission intensity more than hydrogen and that the reduction depends on the NG quality. By utilizing H2‐NG and NH3‐NG mixtures as fuels in ICEs, the emissions can be reduced by 37%–44% and 3%–8%, respectively, compared to engines running on diesel oil or natural gas. The novelty of this study is to demonstrate the potential of cutting GHG emissions in power production using ICEs, new fuel blends, and fulfilling existing fuel requirements agreed on for engines. [ABSTRACT FROM AUTHOR]

Green hydrogen has become more attractive as a fuel for engines to reduce greenhouse gas emissions. By mixing it with natural gas (NG), the modification work on the engine can be minimized but the carbon dioxide emissions from combustion can still be decreased. In this paper, an experimental study was accomplished to investigate the performance of a spark-ignition engine fueled with hydrogen-natural gas blends by either keeping a constant ignition timing or changing it. Up to 25 mol-% hydrogen was mixed into natural gases with different compositions and the methane number and Wobbe index were calculated and compared to the requirements set by Euromot. The results show that up to 15 mol-% hydrogen can be blended into NG to meet the limits of Euromot. However, when 25 mol-% hydrogen was mixed into NG the methane number varied between 56 and 64 depending on the gas composition. This would most likely cause knock for a mixture consisting of higher hydrocarbons but during the executed tests knock was never a problem. Furthermore, it was detected that the methane number alone cannot tell the knock tendency of a gas in a certain engine and an additional condition is needed such as the hydrogen level. An adjusted ignition timing was also preferable compared to a constant one to keep the engine component temperature at a moderate level. • A SI-engine was fueled with different hydrogen-natural gas (H 2 -NG) mixtures. • Wobbe index and methane number (MN) were calculated for all test points. • Efficiency was improved and emissions were decreased with higher hydrogen content. • No tendency of knock when 25 mol-% hydrogen was mixed into natural gas with a low MN. • Additional condition is needed for MN eg. H 2 -level to be sure if knock can happen. [ABSTRACT FROM AUTHOR]